Sayyiduna Abdullah bin al-Shikhkhir says: I came to the Prophet (peace and blessings be upon him), and he would offer (voluntary) prayer both sitting and standing.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator named Sa'id, who narrated from Ghaylan bin Jarir, and from whom Zayd bin al-Hubab narrated; I do not know this narrator. The rest of its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2906